Wood pellet has the potential to reduce dependency on fossil fuels, mitigate global warming and stimulate the forest industries. Economics of wood pellet and impact of carbon tax are examined in this study. The target of the study is space heating energy in the residential, commercial and public sectors in Japan. An energy-economic model in which space heating energy is supplied by wood pellet and kerosene is developed. The model contains market share functions that determine how many customers would choose wood pellet depending on the price competition between wood pellet and kerosene. Model analysis shows the conclusions as follows. Without carbon tax, the pellet price should be less than 35JPY/kg for the market penetration. With 30, 000JPY/tC carbon tax, it becomes 45JPY/kg. Imposing carbon tax leads to an increase in the penetration of pellet except for the case where the pellet price stays at as high level as the current situation. It is also shown that the low cost wood collecting system can drastically increase the utilization of forest biomass such as logging residues and thinned wood in favorable situations. The policy scenario for dissemination of pellet is proposed based on the result of the analysis.
The char morphology after devolatilization and its evolution during gasification plays an important role in determining the coal quality impact on the performance of gasifier. The particle size distribution of devolatilized char affects particle trajectories in gasifier and char entrainment to heat exchanger. The purpose of this study is to propose prediction method of char swelling and shrinking ratio in the early stage of gasification. Swelling and shrinking behavior of single particle was observed using pressurelized laser heater. In order to quantitatively measure the change of particle size, char samples were also produced by drop tube reactor for several types of coal by changing reaction temperature and initial particle size. Moreover, XRD and NMR analyses were carried out to investigate the change of carbon structure during devolatilization. Swelling and shrinking ratio after devolatilization could be described by coal properties, such as volatile matter, ash, carbon, hydrogen, oxygen and maceral content. In particular, vitrinite had large effect on the swelling behavior. The result of XRD and NMR analyses indicated that the development of carbon lamination layer was recognized in plastic range and the hexagonal network extended at solidification stage during devolatiolization.
The effect of flow behavior on degradation of de-NOx catalyst is experimentally and numerically investigated. The de-NOx rate for used catalysts is evaluated using laboratory-scale test apparatus. and the flow behavior in a honeycomb rectangular tube of the catalyst is studied by direct numerical simulations (DNS). The results show that the degradation of the catalyst is enhanced in the upstream region near the inlet. This is due to that the injected flow is a turbulent flow, which facilitates particles in flue gas to attach the catalyst wall, and the flow becomes laminar downstream in the catalyst.